Optical disks often employ grooved media for identifying storage track areas at high track densities. Removal of grooves would be a great advantage. Another factor in optical disk is space utilization; i.e., the less area dedicated to controlling the operation of the recorder using the optical storage medium, the more efficient data storage becomes. Accordingly, it is desired to provide multiple uses of the control area dedicated for controlling a recorder utilizing the storage media.
Many optical disks are so-called hard-sectored; i.e., control information is embossed along radial lines for identifying sectors. The sectors, or the spaces between the embossed areas, circumferentially identify the signal storing tracks. There will be a large number of such tracks on each disk surface. In many optical disks, the storage of data signals intensity modulates a reading light beam such that a single detector can detect both the embossed control area and the data area which can be phase-change modulated, color modulated (using dyes), or ablative recording which introduces pits into the area for representing data signals.
Another form of optical recording is the well-known magnetooptic recording. In magnetooptic recording, the recorded information is sensed by measuring the linear polarization rotation of the reading light beam reflected from the magnetooptic disk. Accordingly, two detectors are required. One for reading the control information and another required for reading the data information. Further, the embossed area requires a relatively large portion of the disk, therefore, it is desired to provide multiple usage of the embossed area for reducing the control signal overhead for the magnetooptic disk. Hereinafter, magnetooptic is identified by the abbreviation "MO".